(a) Field of the Invention
The present invention relates to an apparatus and a method for controlling a mode change of a hybrid electric vehicle. More particularly, the present invention relates to an apparatus and a method for controlling a mode change of a hybrid electric vehicle that changes a mode of the hybrid electric vehicle at an optimal reference point of mode change when a demand power of a driver is stably maintained at greater than a predetermined level.
(b) Description of the Related Art
A hybrid vehicle is a type of vehicle that uses two or more different types of power sources and is generally driven by an engine that obtains a driving torque by burning fuel and a motor that obtains a driving torque with battery power. Hybrid electric vehicles are provided with optimum output torque, based on how the engine and the motor are operated while the vehicles are driven by the two power sources, that is, the engine and the motor.
The hybrid vehicle may be formed in various structures using an engine and an electric motor as a power source, and a transmission mounted electric device (TMED) type hybrid electric vehicle in which a motor is attached to a transmission and in which an engine clutch is inserted between the transmission and the engine may implement an electric vehicle (EV) mode and a hybrid electric vehicle (HEV) mode using disconnection and connection of the engine clutch.
In the TMED type hybrid electric vehicle, a driving mode is changed from the EV mode to the HEV mode when a demand power of a driver is increased. An optimal mode change reference point is determined by considering efficiency of an engine, a motor, and a battery. However, when the demand power of the driver fluctuates near the optimal mode change reference point, a mode change between the EV mode and the HEV mode is generated frequently. In the related art, to prevent a frequent mode change, a hysteresis line is applied to the mode change reference point due to the demand power of the driver. However, when the hysteresis line is applied to the mode change reference point, the demand power and demand power fluctuates, and increasing and decreasing. Thus, an inefficient operation of the engine may be generated.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.